import math as _math
import struct as _struct

from random import uniform as _uniform

from pyglet.media.codecs.base import Source, AudioFormat, AudioData


# Envelope classes:

class _Envelope:
    """Base class for SynthesisSource amplitude envelopes."""

    def get_generator(self, sample_rate, duration):
        raise NotImplementedError


class FlatEnvelope(_Envelope):
    """A flat envelope, providing basic amplitude setting.

    :Parameters:
        `amplitude` : float
            The amplitude (volume) of the wave, from 0.0 to 1.0.
            Values outside this range will be clamped.
    """

    def __init__(self, amplitude=0.5):
        self.amplitude = max(min(1.0, amplitude), 0)

    def get_generator(self, sample_rate, duration):
        amplitude = self.amplitude
        while True:
            yield amplitude


class LinearDecayEnvelope(_Envelope):
    """A linearly decaying envelope.

    This envelope linearly decays the amplitude from the peak value
    to 0, over the length of the waveform.

    :Parameters:
        `peak` : float
            The Initial peak value of the envelope, from 0.0 to 1.0.
            Values outside this range will be clamped.
    """

    def __init__(self, peak=1.0):
        self.peak = max(min(1.0, peak), 0)

    def get_generator(self, sample_rate, duration):
        peak = self.peak
        total_bytes = int(sample_rate * duration)
        for i in range(total_bytes):
            yield (total_bytes - i) / total_bytes * peak
        while True:
            yield 0


class ADSREnvelope(_Envelope):
    """A four part Attack, Decay, Suspend, Release envelope.

    This is a four part ADSR envelope. The attack, decay, and release
    parameters should be provided in seconds. For example, a value of
    0.1 would be 100ms. The sustain_amplitude parameter affects the
    sustain volume. This defaults to a value of 0.5, but can be provided
    on a scale from 0.0 to 1.0.

    :Parameters:
        `attack` : float
            The attack time, in seconds.
        `decay` : float
            The decay time, in seconds.
        `release` : float
            The release time, in seconds.
        `sustain_amplitude` : float
            The sustain amplitude (volume), from 0.0 to 1.0.
    """

    def __init__(self, attack, decay, release, sustain_amplitude=0.5):
        self.attack = attack
        self.decay = decay
        self.release = release
        self.sustain_amplitude = max(min(1.0, sustain_amplitude), 0)

    def get_generator(self, sample_rate, duration):
        sustain_amplitude = self.sustain_amplitude
        total_bytes = int(sample_rate * duration)
        attack_bytes = int(sample_rate * self.attack)
        decay_bytes = int(sample_rate * self.decay)
        release_bytes = int(sample_rate * self.release)
        sustain_bytes = total_bytes - attack_bytes - decay_bytes - release_bytes
        decay_step = (1 - sustain_amplitude) / decay_bytes
        release_step = sustain_amplitude / release_bytes
        for i in range(1, attack_bytes + 1):
            yield i / attack_bytes
        for i in range(1, decay_bytes + 1):
            yield 1 - (i * decay_step)
        for i in range(1, sustain_bytes + 1):
            yield sustain_amplitude
        for i in range(1, release_bytes + 1):
            yield sustain_amplitude - (i * release_step)
        while True:
            yield 0


class TremoloEnvelope(_Envelope):
    """A tremolo envelope, for modulation amplitude.

    A tremolo envelope that modulates the amplitude of the
    waveform with a sinusoidal pattern. The depth and rate
    of modulation can be specified. Depth is calculated as
    a percentage of the maximum amplitude. For example:
    a depth of 0.2 and amplitude of 0.5 will fluctuate
    the amplitude between 0.4 an 0.5.

    :Parameters:
        `depth` : float
            The amount of fluctuation, from 0.0 to 1.0.
        `rate` : float
            The fluctuation frequency, in seconds.
        `amplitude` : float
            The peak amplitude (volume), from 0.0 to 1.0.
    """

    def __init__(self, depth, rate, amplitude=0.5):
        self.depth = max(min(1.0, depth), 0)
        self.rate = rate
        self.amplitude = max(min(1.0, amplitude), 0)

    def get_generator(self, sample_rate, duration):
        total_bytes = int(sample_rate * duration)
        period = total_bytes / duration
        max_amplitude = self.amplitude
        min_amplitude = max(0.0, (1.0 - self.depth) * self.amplitude)
        step = (_math.pi * 2) / period / self.rate
        for i in range(total_bytes):
            value = _math.sin(step * i)
            yield value * (max_amplitude - min_amplitude) + min_amplitude
        while True:
            yield 0


# Waveform generators

def silence_generator(frequency, sample_rate):
    while True:
        yield 0


def noise_generator(frequency, sample_rate):
    while True:
        yield _uniform(-1, 1)


def sine_generator(frequency, sample_rate):
    step = 2 * _math.pi * frequency / sample_rate
    i = 0
    while True:
        yield _math.sin(i * step)
        i += 1


def triangle_generator(frequency, sample_rate):
    step = 4 * frequency / sample_rate
    value = 0
    while True:
        if value > 1:
            value = 1 - (value - 1)
            step = -step
        if value < -1:
            value = -1 - (value - -1)
            step = -step
        yield value
        value += step


def sawtooth_generator(frequency, sample_rate):
    period_length = int(sample_rate / frequency)
    step = 2 * frequency / sample_rate
    i = 0
    while True:
        yield step * (i % period_length) - 1
        i += 1


def pulse_generator(frequency, sample_rate, duty_cycle=50):
    period_length = int(sample_rate / frequency)
    duty_cycle = int(duty_cycle * period_length / 100)
    i = 0
    while True:
        yield int(i % period_length < duty_cycle) * 2 - 1
        i += 1


# Source classes:

class SynthesisSource(Source):
    """Base class for synthesized waveforms.

    :Parameters:
        `generator` : A non-instantiated generator object
            A waveform generator that produces a stream of floats from (-1, 1)
        `duration` : float
            The length, in seconds, of audio that you wish to generate.
        `sample_rate` : int
            Audio samples per second. (CD quality is 44100).
        `envelope` : :py:class:`pyglet.media.synthesis._Envelope`
            An optional Envelope to apply to the waveform.
    """
    def __init__(self, generator, duration, sample_rate=44800, envelope=None):
        self._generator = generator
        self._duration = duration
        self.audio_format = AudioFormat(channels=1, sample_size=16, sample_rate=sample_rate)

        self._envelope = envelope or FlatEnvelope(amplitude=1.0)
        self._envelope_generator = self._envelope.get_generator(sample_rate, duration)

        # Two bytes per sample (16-bit):
        self._bytes_per_second = sample_rate * 2
        # Maximum offset, aligned to sample:
        self._max_offset = int(self._bytes_per_second * duration) & 0xfffffffe
        self._offset = 0

    def get_audio_data(self, num_bytes, compensation_time=0.0):
        """Return `num_bytes` bytes of audio data."""
        num_bytes = min(num_bytes, self._max_offset - self._offset)
        if num_bytes <= 0:
            return None

        timestamp = self._offset / self._bytes_per_second
        duration = num_bytes / self._bytes_per_second
        self._offset += num_bytes

        # Generate bytes:
        samples = num_bytes >> 1
        generator = self._generator
        envelope = self._envelope_generator
        data = (int(next(generator) * next(envelope) * 0x7fff) for _ in range(samples))
        data = _struct.pack(f"{samples}h", *data)

        return AudioData(data, num_bytes, timestamp, duration, [])

    def seek(self, timestamp):
        # Bound within duration & align to sample:
        offset = int(timestamp * self._bytes_per_second)
        self._offset = min(max(offset, 0), self._max_offset) & 0xfffffffe
        self._envelope_generator = self._envelope.get_generator(self.audio_format.sample_rate, self._duration)


class Silence(SynthesisSource):
    def __init__(self, duration, frequency=440, sample_rate=44800, envelope=None):
        """Create a Silent waveform."""
        super().__init__(silence_generator(frequency, sample_rate), duration, sample_rate, envelope)


class WhiteNoise(SynthesisSource):
    def __init__(self, duration, frequency=440, sample_rate=44800, envelope=None):
        """Create a random white noise waveform."""
        super().__init__(noise_generator(frequency, sample_rate), duration, sample_rate, envelope)


class Sine(SynthesisSource):
    def __init__(self, duration, frequency=440, sample_rate=44800, envelope=None):
        """Create a sinusoid (sine) waveform."""
        super().__init__(sine_generator(frequency, sample_rate), duration, sample_rate, envelope)


class Square(SynthesisSource):
    def __init__(self, duration, frequency=440, sample_rate=44800, envelope=None):
        """Create a Square (pulse) waveform."""
        super().__init__(pulse_generator(frequency, sample_rate), duration, sample_rate, envelope)


class Triangle(SynthesisSource):
    def __init__(self, duration, frequency=440, sample_rate=44800, envelope=None):
        """Create a Triangle waveform."""
        super().__init__(triangle_generator(frequency, sample_rate), duration, sample_rate, envelope)


class Sawtooth(SynthesisSource):
    def __init__(self, duration, frequency=440, sample_rate=44800, envelope=None):
        """Create a Sawtooth waveform."""
        super().__init__(sawtooth_generator(frequency, sample_rate), duration, sample_rate, envelope)


#############################################
#   Experimental multi-operator FM synthesis:
#############################################

def sine_operator(sample_rate=44800, frequency=440, index=1, modulator=None, envelope=None):
    """A sine wave generator that can be optionally modulated with another generator.

    This generator represents a single FM Operator. It can be used by itself as a
    simple sine wave, or modulated by another waveform generator. Multiple operators
    can be linked together in this way. For example::

        operator1 = sine_operator(samplerate=44800, frequency=1.22)
        operator2 = sine_operator(samplerate=44800, frequency=99, modulator=operator1)
        operator3 = sine_operator(samplerate=44800, frequency=333, modulator=operator2)
        operator4 = sine_operator(samplerate=44800, frequency=545, modulator=operator3)

    :Parameters:
        `sample_rate` : int
            Audio samples per second. (CD quality is 44100).
        `frequency` : float
            The frequency, in Hz, of the waveform you wish to generate.
        `index` : float
            The modulation index. Defaults to 1
        `modulator` : sine_operator
            An optional operator to modulate this one.
        `envelope` : :py:class:`pyglet.media.synthesis._Envelope`
            An optional Envelope to apply to the waveform.
    """
    # FM equation:  sin((i * 2 * pi * carrier_frequency) + sin(i * 2 * pi * modulator_frequency))
    envelope = envelope or FlatEnvelope(1).get_generator(sample_rate, duration=None)
    sin = _math.sin
    step = 2 * _math.pi * frequency / sample_rate
    i = 0
    if modulator:
        while True:
            yield sin(i * step + index * next(modulator)) * next(envelope)
            i += 1
    else:
        while True:
            yield sin(i * step) * next(envelope)
            i += 1


def composite_operator(*operators):
    return (sum(samples) / len(samples) for samples in zip(*operators))
